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Cooperation of GGAs and AP-1 in Packaging MPRs at the Trans-Golgi Network

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Science  06 Sep 2002:
Vol. 297, Issue 5587, pp. 1700-1703
DOI: 10.1126/science.1075327

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Abstract

The Golgi-localized, γ-ear–containing, adenosine diphosphate ribosylation factor–binding proteins (GGAs) are multidomain proteins that bind mannose 6-phosphate receptors (MPRs) in the Golgi and have an essential role in lysosomal enzyme sorting. Here the GGAs and the coat protein adaptor protein–1 (AP-1) were shown to colocalize in clathrin-coated buds of the trans-Golgi networks of mouse L cells and human HeLa cells. Binding studies revealed a direct interaction between the hinge domains of the GGAs and the γ-ear domain of AP-1. Further, AP-1 contained bound casein kinase–2 that phosphorylated GGA1 and GGA3, thereby causing autoinhibition. This could induce the directed transfer of the MPRs from GGAs to AP-1. MPRs that are defective in binding to GGAs are poorly incorporated into AP-1–containing clathrin-coated vesicles. Thus, the GGAs and AP-1 interact to package MPRs into AP-1–containing coated vesicles.

  • * These authors contributed equally to this work.

  • Present address: Genome Institute of Singapore, 1 Science Park Road, The Capricorn #05-01 Singapore 117528.

  • To whom correspondence should be addressed. E-mail: skornfel{at}im.wustl.edu

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